1.7 Relay Terms and Definitions-Glossary

The following definitions do not include terms peculiar to mathematical formula, statistical analysis, relay reliability studies, and the like. Such terms are defined in the appropriate chapter. When cross-references are made, the preferred terminology is the one under which the definition appears.

Seating. The magnetic positioning of an armature in its final desired location.
Self de-energize. The removal of power from a relay coil by an auxiliary switch or contact within the relay itself. Usually applies to latching relays only.
Self de-energizing switch. A secondary relay or auxiliary contact usually enclosed within the primary relay which removes power from the primary relay coil after it has transferred position. Usually applies to latching relays only.
Sensitivity. Specified pickup expressed in watts.
Separation, contact. See gap, contact.
Sequence, contact. The order in which contacts open and close in relation to other contacts and armature motion.
Set, contact. See combination, contact.
Shading coil. See ring, shading.
Shield, electrostatic. Grounded conducting member located between two or more mutually insulated elements to minimize electrostatic coupling.
Shield, magnetic. A ferromagnetic member used to reduce magnetic coupling.
Shim, nonmagnetic. A nonmagnetic member introduced in series with the magnetic circuit. See residual.
Sleeve, coil. A conducting tube placed around the full length of the coil core as a shortcircuited winding to retard the establishment or decay of flux within the magnetic path.
Slow-release time characteristic. See characteristic, slow release time.
Slug, coil. A conducting tube placed around a portion of the core to retard the establishment or decay of flux within the magnetic path.
Soak magnetic. The conditioning of a relay to a predetermined magnetic state (usually saturation).
Soak value, magnetic. The voltage, current, or power applied to the relay coil to ensure a predetermined magnetic state (usually saturation).
Solenoid relay. See relay, plunger.
Spring, armature. See contact movable.
Spring, balance. A member used in relays with permissive make contacts to provide restoring force.
Spring, brush. The spring in a rotary stepping-switch bank that contacts the associated wiper.
Spring, buffer. See spring, damper.
Spring compliant (contact). A contact spring that moves appreciably when mating contact spring.
Spring, contact. A current-carrying spring to which a contact is fastened or which in itself serves as a contact.
Spring, damper. An auxiliary spring added to prevent unwanted movement of some relay member because of vibration or shock.
Spring, driving. The spring that drives the wipers of a stepping relay or stepping switch.
Spring, noncompliant (contact). A contact spring that does not move appreciably when contacted by a mating contact spring.
Spring, restoring. See spring return.
Spring, retractile. See spring, return.
Spring, return. A spring that moves or tends to move the armature to the released (normal) position; i.e., a spring that provides a force to move the armature to the released (normal) position and hold it there.
Stack. See pileup.
Stack contact. See pileup, contact.
Start. A relay starts at the instant it leaves an initial condition. (IEC)
Step, applied power. The sudden application of RMS load voltage to the relay when in the off condition.
Stop, nonmagnetic armature. See residual.
Stop, spring. A member that controls the position of a pretensioned spring.
Stroke. See travel, armature.
Stud, armature. See buffer, armature.
Stud, spring. Stud, gap. See gap, buffer.
Switch. A relay switches at the instant it completes its designated function in a given output circuit. (IEC)
Switch, crossbar. A switching device employing multiple relay elements in a matrix of grid arrangement to connect selected crosspoints electrically.
Switch, dry reed. See contact, reed. Switch, stepping. A class of electromagnetically operated, multiposition switching devices. Their wipers are rotated in steps so that contact is successively made between the wiper tips and contacts that are separated electrically and mounted in a circular arc called a bank.
Temperature case (TC). The temperature at a specified point on the relay which is used to evaluate the current capabilities of the relay.
Temperature, maximum, allowable case (TC max). The maximum allowable case temperature for a given load current at rated line voltage.
Temperature, maximum junction TJ(MAX). The maximum junction temperature of the output switching semiconductors, expressed in ° C. (Applies to solid state relays.)
Temperature, operating (TA). The ambient temperature range over which operation is specified with relays unmounted or mounted to a heat sink as specified.
Temperature, storage (TSTG). The ambient temperature range to which a nonoperating relay may be subjected without permanent electrical or mechanical damage.
Terminal contact spring. The portion of a contact spring to which the current-carrying conductors are attached.
Terminal coil. A device such as a solder lug, tab, binding post, or similar fitting, on which the coil winding lead is terminated and to which the coil power supply is connected.
Thermal resistance maximum, junction to ambient (ROJA). The maximum thermal resistance between the semiconductor junction and still air ambient. (Expressed in ° C/watt).
Thermal resistance maximum, junction to case (ROJC). The maximum thermal resistance between the output switch semiconductor(s) junction to point of measurement on the relay case (expressed in ° C/watt).Thermal shock non-operating. These temperature extremes between which the relay may be rapidly cycled without permanent electrical or mechanical damage.
Time, actuation. The time interval from coil energization or de-energization to the functioning of a specified contact; same as time, contact actuation, subdivided as follows:
(1)Time, final actuation-The sum of the initial actuation time and the contact bounce intervals following such actuation.
(2)Time, initial actuation-The time from coil energization or de- energization to the first closing of a previously open contact or the first opening of a previously closed contact. (See time, operate; time, release.)
Time, bridging. The time in which all contacts of a continuity transfer combination are electrically connected during the transfer.
Time, contact bounce. The time interval from initial actuation of a contact to the end of bounce.
Time, contact stagger. The time interval between the functioning of contacts on the same relay.(For example, the time difference between the opening of two normally closed contacts on pickup.)
Time, operate. (1) The time interval from coil energization to the functioning of the last contact to function. Where not otherwise stated, the functioning time of the contact in question is taken as its initial actuation time (that is, it does not include contact bounce time). (See Figures 1.01 and 1.02.) (2) For a solid state or hybrid relay in a non-operated state, the time from the application of the pickup voltage to the change of state of the output.
Time, release. (1) The time interval from coil de-energization to the functioning of the last contact to function. Where not otherwise stated, the functioning time of the contact in question is taken as its initial actuation time (that is, it does not include contact bounce time). (2) For a solid state or hybrid relay in an operated state, the time from the application of the dropout voltage to the change of state of the output.
Time, seating. The time interval from coil energization to the seating of the armature.
Time transfer. The time interval between opening the closed contact and closing the open contact of a break-before-make contact combination.
Travel, armature. The distance traveled during operation by a specified point on the armature.
Trip pulse. A short, high level pulse applied to the tip coil of a latching relay.
Trip, to trip. A latching relay trips when it changes from the operated to the unoperated condition. Usually refers to the breaking of continuity of the main contacts.
Trip value, specified. As the current or voltage on an operated latching relay is step applied, the value at or below which all contacts return to their unoperated positions.
Tube, coil. An insulated tube on which a coil is wound.
Unergized condition. The specified condition of an unergized monostable relay. (IEC)
Vibration, nonoperating. The vibration level and frequency span to which the relay may be subjected without permanent electrical or mechanical damage.
Voltage, nominal A single value of voltage (or a narrow voltage range) intended to be applied to the coil or input. See voltage, rated coil.
Voltage, off state. In solid state relay, the following determine whether the relay will stay off under each load voltage condition:
(1) Critical rate of rise of commutation voltage, dv/dt. The maximum value of the rate of rise of principal voltage which will cause switching from the off state to the on state.
(2) Maximum off state voltage (VDMax)(RMS). The maximum effective steady state voltage that the output is capable of withstanding when in off state.
(3) Maximum rate of rise of off state voltage, dv/dt. The rate of rise of the off-state voltage which the output can withstand without false operation.
(4) Minimum off state voltage (VDMin)(RMS). The minimum effective voltage which the relay will switch.
(5) Non-repetitive peak voltage (VDSM).The maximum off-state voltage that the output terminals are capable of withstanding without breakover or damage.
Voltage, on state. In solid state relays, the output terminal wave form at rated current consists of repetitive half-cycles (+and-) of distinctive voltage drops. Each voltage state is necessary for load current conduction and may be specified for specific applications, as follows:
(1) Instantaneous on state voltage (VT) The instantaneous voltage across the output when in the on condition.
(2) Maximum RMS on state voltage (VT)(RMS). Maximum RMS voltage drop across the relay output at maximum load current ITRMS.
(3) Minimum power factor load (PFMIN). The minimum power factor load the relay will switch and still meet all of its electrical specifications.
(4) Peak on state voltage (VTM). The maximum value of VT excluding ± 20° of zero crossing of the voltage wave form.
Voltage, rated coil. The coil voltage at which the relay is intended to operate for the prescribed duty cycle. Note: The use of any coil voltage less than rated may compromise the performance of the relay.
Voltage, reverse polarity. The maximum allowable reverse voltage which may be applied to the input of a solid state relay without permanent damage.
Winding. An electrically continuous length of insulated wire wound on a bobbin, spool or form.
Winding, bias. An auxiliary winding to produce an electromagnetic bias.
Winding, bifilar. Two windings with the wire of each winding alongside the other, matching turn for turn; may be either inductive or noninductive. (See coil, parallel wound.)
Winding, noninductive. A winding in which the magnetic fields produced by two parts of the winding cancel each other and provide noninductive resistance.
Wipe, contact. The sliding or tangential motion between two mating contact surfaces as they open or close.
Wiper. The moving contact on a rotary stepping switch.
Zero-voltage-turn-on voltage (zero synchronous turn-on) (VTO). The maximum voltage across the output terminals following initial turn-on.